Among the following choose the one that has diplontic life cycle.
Fucus is a brown alga with haploid gametophytic stage limited to only gametes. It has multicellular sporophyte. Hence the life cycle of Fucus is diplontic. The life cycle of Laminaria, Porphyra and Polysiphonia is haplodiplontic as they have multicellular gametophytes and sporophytes.